Abstract
Magnon systems used in quantum devices require low damping if coherence is to be maintained. The ferrimagnetic electrical insulator yttrium iron garnet (YIG) has low magnon damping at room temperature and is a strong candidate to host microwave magnon excitations in future quantum devices. Monocrystalline YIG films are typically grown on gadolinium gallium garnet (GGG) substrates. In this work, comparative experiments made on YIG waveguides with and without GGG substrates indicate that the material plays a significant role in increasing the damping at low temperatures. Measurements reveal that damping due to temperature-peak processes is dominant above 1 K. Damping behavior that we show can be attributed to coupling to two-level fluctuators (TLFs) is observed below 1 K. Upon saturating the TLFs in the substrate-free YIG at 20 mK, linewidths of ∼1.4 MHz are achievable: lower than those measured at room temperature.
Highlights
Microwave magnonic systems have been subject to extensive experimental studies for decades
Enthusiasm has grown for the study of magnon dynamics at millikelvin temperatures, the temperature regime in which solid-state microwave quantum systems operate
The behavior of GGG at millikelvin temperatures is yet to be thoroughly characterized,26–28 but recent results at millikelvin temperatures have suggested that magnon damping in YIG films grown on GGG is higher than expected if the properties of the YIG system alone are considered
Summary
Cite as: APL Mater. 7, 101120 (2019); https://doi.org/10.1063/1.5115266 Submitted: 16 June 2019 • Accepted: 29 September 2019 • Published Online: 24 October 2019 ARTICLES YOU MAY BE INTERESTED IN Introduction to antiferromagnetic magnons Journal of Applied Physics 126, 151101 (2019); https://doi.org/10.1063/1.5109132 Hybrid magnonics: Physics, circuits, and applications for coherent information processing Journal of Applied Physics 128, 130902 (2020); https://doi.org/10.1063/5.0020277 A quantum engineer's guide to superconducting qubits Applied Physics Reviews 6, 021318 (2019); https://doi.org/10.1063/1.5089550
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